A sizable fraction of ignitions of structures, resulting in serious fires, are due to electrical distribution problems. Every year, these electrical fires account for many deaths and injuries, and millions of dollars in direct property damage. The cause of many electrical distribution problems can be attributed to faulty wirings, cords and plugs. The malfunctioning of these components often lead to overheating or sudden generation of sparks that can potentially cause fires and even explosions. The source of such malfunctions can be varied, stemming from arcing, short circuits, poor connections or sudden rupturing and shearing of cables caused by tensile forces.
An electric arc can be defined as formation of a channel of hot ionized plasma gas that is highly conductive. This causes an electrical breakdown, resulting in a flow of current between contacts separated by small gaps, even in instances where they are separated by insulative coating or a nonconductive media such as air. An unintended electric arc or alternatively arc flash, can be particularly detrimental to electric power transmission and distribution systems. In addition, an electrical arc can result in very high temperatures that melts most material and poses serious threats of injury. Devices which may cause arcing include switches, circuit breakers, relay contacts, fuses and cables, especially cables with poor terminations.
Short circuits are caused when there is a surge of current in an unintended part of a circuit or a network. When an abnormally low resistance connection is created between two nodes that are meant to be kept at different voltages, charges flow quickly along this different and unintendedly formed path. The sudden flow of excessive electric current leads to overheating of the device and the surrounding areas, potentially causing fires and explosions. Short circuits are most likely to occur between conductors of two different phases, such as that of voltage/power phases and neutral/ground phases. It is, however, possible for short circuits to arise between two conductors of the same phase.
A number of conditions can cause an unintentional short circuit. Some examples are structurally damaged or bent metal components like prongs and socket contacts, stalled motors, and jammed pumps/fans caused by debris. Short circuits can also be caused by worn insulations, such as on wires, cables and other electrical components. For example, a worn wire insulation in a battery cell can expose the underlying metal and create a path between positive and negative terminals. The ensuing low resistance across this connection then causes a large amount of energy to be dispersed quickly. The rapid buildup of associated heat can lead to fires/explosions that can release hydrogen gas and electrolytes and/or cause chemical exposures to acids or base fluids.
In the airline industry, electrical fires are a source of major concern not just in the air, but more importantly on the ground. Aircraft ground power assemblies are required to deliver ground power to aircrafts when parked or when in hangers undergoing inspection and repair. Faulty electrical distribution in these assemblies can lead to disastrous results. Proximity to large amounts of highly combustible jet fuel creates an excessive risk of damage and injury to nearby structures and individuals. In airports located close to densely populated areas, contamination issues and potential for complete infrastructural collapse further exacerbates this risk.
In recent years, electrical fires have been more frequently caused by faulty cables/plugs and worn insulations. Shearing and rupturing of cables can cause sparks and short circuits. In addition, misalignment of contacts caused by prolongued use, overheating or sudden forces experienced during engagement and disengagement of devices can also lead to electrical malfunctions. Consequently, minimizing the risk of electrical shorts and other related conditions caused by faulty cables and plugs is desired, especially when such components are utilized in assemblies that supply ground power to aircrafts.